used it for the first time today. Witha the moto 950 mah car charger. Did not notice that it quit charging or anything but after 2 hours I noticed on LTE and GPS I was at 76% when I got out of the car not really sure what the starting number was. Will try it again. Then will try it with lte disabled to see if that helps any.

I took my new Droid Charge on a driving vacation the last couple weeks and hit this problem big time. When in the direct sun, this display stays at full brightness. I found that the battery would drain, even though the charger is plugged in! Then when the battery got near empty - I got this warning pop-up that charging was suspended due to overheating.
I was able to work around this problem two ways:
1. The phone was near an A/C vent - I turned the vent downward to blow across the phone.
2. I was often on long stretches of highway - where the next turn guidance might be 20+ minutes away. So I would hit the power button on top of the display to turn it off. then make a mental note of about how long it will be. It turns out the mental note wasn't too important - the navigator was still running and it still gave me the voice prompt well before the next maneuver. So then I just hit the power button to wake the display back up.

One nice feature - I have screen lock enabled on my phone - but if the navigator was running when I turned the screen off - then when I turned it back on, it bypassed the screen lock and went right back into the navigator - so very little distraction to my driving!

Also, with the screen off - the battery was able to recharge - so with this mode of operations (turning off the display for long stretches) I was able to keep the battery at 100%

I'll mention it hear, but it belongs in another topic - I discovered that if I plugged my headset in to listen to audio - while navigating in the car - that I would occationally get a "GPS signal lost" pop-up - and a stall in navigation - it typically would re-sync in about a minute. This only occurs with the headset plugged in.

Also, make sure to plug it into the main car power outlet, not aux one. I had my phone with GPS on for about 3 hours straight, stayed at 100% battery life and no overheating. Plugged it into the aux port, and it went up to 56%, overheated and quit charging. Had to cool it off with AC.